Connected: An Internet Encyclopedia
RFC 1850 - 3.13. OSPF Route Table Use

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### 3.13. OSPF Route Table Use

    --  OSPF Use of the CIDR Route Table

    ospfRouteGroup           OBJECT IDENTIFIER ::= { ospf 13 }

    -- The IP Forwarding Table defines a number of objects for use by
    -- the routing protocol to externalize its information.  Most of
    -- the variables (ipForwardDest, ipForwardMask, ipForwardPolicy,
    -- ipForwardNextHop, ipForwardIfIndex, ipForwardType,
    -- ipForwardProto, ipForwardAge, and ipForwardNextHopAS) are
    -- defined there.

    -- Those that leave some discretion are defined here.

    -- ipCidrRouteProto is, of course, ospf (13).

    -- ipCidrRouteAge is the time since the route was first calculated,
    -- as opposed to the time since the last SPF run.

    -- ipCidrRouteInfo is an OBJECT IDENTIFIER for use by the routing
    -- protocol.  The following values shall be found there depending
    -- on the way the route was calculated.

    ospfIntraArea      OBJECT IDENTIFIER ::= { ospfRouteGroup 1 }
    ospfInterArea      OBJECT IDENTIFIER ::= { ospfRouteGroup 2 }
    ospfExternalType1  OBJECT IDENTIFIER ::= { ospfRouteGroup 3 }
    ospfExternalType2  OBJECT IDENTIFIER ::= { ospfRouteGroup 4 }

    -- ipCidrRouteMetric1 is, by definition, the primary routing
    -- metric.  Therefore, it should be the metric that route
    -- selection is based on.  For intra-area and inter-area routes,
    -- it is an OSPF metric.  For External Type 1 (comparable value)
    -- routes, it is an OSPF metric plus the External Metric.  For
    -- external Type 2 (non-comparable value) routes, it is the
    -- external metric.

    -- ipCidrRouteMetric2 is, by definition, a secondary routing
    -- metric.  Therefore, it should be the metric that breaks a tie
    -- among routes having equal metric1 values and the same
    -- calculation rule.  For intra-area, inter-area routes, and
    -- External Type 1 (comparable value) routes, it is unused.  For
    -- external Type 2 (non-comparable value) routes, it is the metric
    -- to the AS border router.

    -- ipCidrRouteMetric3, ipCidrRouteMetric4, and ipCidrRouteMetric5 are
    -- unused.

Next: 3.14. OSPF Area Aggregate Table

Connected: An Internet Encyclopedia
RFC 1850 - 3.13. OSPF Route Table Use